Power converters are used in a variety of portable electronic devices, including laptops, mobile devices, cellular phones, electronic digital pads, video cameras, digitals cameras, and the like. In addition, power converters may be used in non-portable applications, such as liquid-crystal display (LCD) backlighting, automotive lighting, and other general purpose or specialty lighting.
Power converters come in many forms. Some converters are AC-DC converters, which convert an alternating current (AC) input voltage to a DC output voltage. A DC-DC converter typically converts one input DC input voltage to a different DC output voltage.
Conventional AC-DC power converters typically include a diode bridge rectifier stage (i.e., a bridge or full-wave rectifier) and a bulk storage capacitor. The incoming AC voltage is generally provided by an AC power supply or AC line, which is converted to a DC output voltage when run through the diode bridge rectifier and bulk storage capacitor. This DC voltage is typically further processed by a converter, which generates an output DC voltage that is applied across a load, such as an array of individual LEDs (i.e., “LED array”).
Using LEDs for lighting applications is becoming more and more popular as the cost of LEDs drops due to manufacturing improvements. LED lighting often utilizes an LED array, such as a plurality of LEDs connected in series, to increase the amount of light output to a desired amount. Because LEDs typically operate from a DC voltage source, the AC voltage that is typically available as a power source needs to be converted to DC power in order to drive the LED array, and thus an LED driver is provided to manage and control the DC power supplied to the LED array.
Conventionally, an LED driver includes a flyback or boost DC-DC converter that receives, as an input, the rectified DC voltage output from the AC-DC converter and is then used to provide the suitable voltage and current, as an output from the DC-DC converter, to the LED load.
However, the voltage at which an LED array operates is often much higher than the operating voltage of other circuitry components within the LED driver or other components external to the LED driver. Including additional circuitry within the LED driver, to supply a range of voltages to operate both the LED array and other auxiliary components, increases the weight, complexity, and cost to the LED driver.